The availability of electrical devices during fires can have lifesaving implications. Exit signs and emergency lights help light where to go in an emergency. Hard-wired fire alarms alert people to an emergency situation. In hospitals and nursing homes, electricity is needed to power devices that are directly in use to sustain life. For these and other reasons, government regulations in numerous countries now specify that essential electrical circuits be protected in order to ensure that the electrical system maintain an operating condition during a fire to ensure the safety of persons inside the building and also to permit fire-fighting personnel to be more efficient in controlling and extinguishing fires. For example, in certain locations, such as high-rise buildings, a minimum amount of time is required for fire alarms to sound and flash so that all persons are alerted. Therefore, the electrical system during the fire must remain intact at least during such critical periods to allow the electrical fire alarms to continue in operation.
Along such lines, it has been established that some essential electrical circuits must be capable of operating for at least one hour, and in some other cases two hours or more to ensure safety of people. As noted, such systems include fire alarm systems, and may also include telephone systems, lighting systems, elevator systems, ventilation systems, water pumps, and other electrically powered lifesaving systems. It may also include voice systems to allow communication during a fire for evacuation of personnel or to allow fire fighters to talk to one another during a fire. Other essential circuits include control and power circuits for fireman's elevators and those fans and dampers which evacuate smoke or shut off smoke leaking into other areas. In addition, automatic door locks, emergency lighting, generators, fire pumps, strobes, smoke detectors, etc., may also similarly require appropriate insulation so that they will remain functional a minimum period of time in a fire situation.
Presently, non fire-rated electrical wires are at risk in a fire-related emergency. Non fire-rated wiring is not designed to sustain operation at high temperatures. Non fire-rated wiring insulation will quickly degrade in a high temperature environment as may exist in a fire.
Several types of fire-rated electrical cables are currently manufactured in a variety of ways. However, all of these fire-rated electrical cables are limited in that splicing the electrical cables in the field (a location where the wiring is performed) negates the fire rating. More simply, splicing technology has not been developed that reliably prevents a fire-rated electrical cable from breaking down at the splice in a high temperature environment. As a result, safety code prohibits fire-rated electrical cables from being spliced in the field. This code limitation often forces electrical contractors to run hundreds of feet of electrical cable without interruption. Non-rated electrical cables, in contrast, often have long runs interrupted by splices in junction boxes to make pulling the wire less difficult. Pulling long runs of fire-rated electrical cable is more labor intensive and, if performed improperly, can lead to damaging the fire-rated electrical cables. In some situations, fire-rated electrical cables are needed in lengths exceeding normal manufacture, which requires custom manufacturing of a fire-rated electrical cable. Non-rated electrical cables do not have the same problem because of the option to splice together multiple sections of electrical cable. It would be advantageous to device a method of splicing a fire-rated electrical cable that would not impinge on the rating of the fire-rated electrical cable.
In fact, currently no fire-rated electrical cable is approved for field splicing. Splicing involves making a connection between two electrical cables. Splicing requires the electricians to tear back the insulation of the electrical cable, electrically connect the conductors, and apply insulation and a jacket to the spliced area. Splicing Mineral Insulated (“MI”) electrical cable can only be performed at factories because of the complex nature of splicing mineral insulated electrical cable. A fire-rated electrical cable that could be spliced in the field would reduce costs for installing fire-rated electrical cables.
An important performance characteristic of a fire-rated electrical cable structure is its ability, in general, to withstand temperatures in the neighborhood of 1850° F. for about a two hour duration and subsequent water spray exposure with mechanical vibration resulting from the water spray. Pursuant to the fire-rated electrical cable requirements of UL 2196, for instance, a fire-rated electrical cable structure should provide a functional circuit throughout the required fire testing period of exposure. UL 2196 provides a test method to monitor electrical cable circuit integrity with the ASTM E 119 temperature profile, which gradually raises the temperature to 1000° F. at 5 minutes into the test, to 1700° F. at 1 hour, and 1850° F. at 2 hours. In addition, UL 2196 provides a mandatory “hose stream test” which is conducted on the fire test sample within 3 minutes after the fire test. Two levels of hose stream exposures are defined. Application of the lesser impact hose stream test is limited to fire alarm electrical cable. Fire alarm electrical cable must also comply with Article 760 of the National Electric Code, whose requirements are also incorporated herein by reference.
Thus, a heretofore unaddressed need exists in the industry to address the aforementioned deficiencies and inadequacies.